1. Field of the Invention
This invention relates to a safety valve and hydraulic actuator and more particularly to a safety valve for controlling flow in a well line and to a hydraulic actuator for controlling the operation of the safety valve. The hydraulic actuator is designed to be operated in conjunction with a pilot valve having an exhaust port.
2. The Prior Art
The combination of a safety valve, hydraulic actuator for the safety valve, and a pilot valve to control the actuator is disclosed by U.S. Pat. No. 2,693,819 to Otis.
Hydraulic actuators for safety valve may take the form of a type U or type UX Otis hydraulic actuator illustrated on pages 4026 and 4028 of the 1974-1975 "COMPOSIT CATALOGUE OF OIL FIELD EQUIPMENT & SERVICES" or the Baker HYDRA-MATIC actuator illustrated on page 387 of the 1974-1975 "COMPOSIT CATALOGUE OF OIL FIELD EQUIPMENT & SERVICES."
However the above actuators have one main problem. They are designed to be operated by a pilot valve that vents the control pressure to the atmosphere. In recent years, increased environmental concern has led to an attempt to provide an actuator-pilot valve system wherein the pilot valve does not vent the control pressure to the atmosphere. However, many pilot valves do include an exhaust port through which control pressure is vented to the atmosphere. For example, see U.S. Pat. Nos. 2,986,157 to Dollison; 3,026,904 to Dollison; and 3,621,881 to Vicari and the type P, type B, and type D, pilots illustrated on pages 4031 and 4033 of the 1974-1975 "COMPOSIT CATALOGUE OF OIL FIELD EQUIPMENT & SERVICES."
To eliminate the exhaust of control fluids, ventless pilot valves have been utilized in combination with a safety valve. For example, see U.S. Pat. Nos. 2,843,371 to Liljestrand; 3,092,136 to Willis; and 3,800,822 to Baker. One problem with the structure disclosed in the last two mentioned patents is that they require the use of a single safety valve, actuator, and pilot valve combination. There is little, if any, interchangeability between the type of safety valves, actuators, and pilot valves that may be utilized in the combination.